The present invention relates to a magnetic disc device wherein a magnetic disc is housed in a casing.
A magnetic disc device as illustrated in U.S. Ser. No. 292,447 will first be described with reference to FIGS. 1 and 2A and 2B, in which FIG. 1 is an exploded perspective view of the device and FIGS. 2A and 2B are respectively a top view and a bottom view of the same. Referring to these figures, a f1exible magnetic disc 1 consists of a thin, disc-shaped base film of a high polymeric material and a magnetic layer uniformly formed on the bottom surface of the base film. A center core 2 is fitted in a circular hole at the center of the magnetic disc 1 through a ring-shaped double-coated adhesive tape 3. The center core 2 has a flange 4 and is formed by pressing a thin metal plate. The magnetic disc 1 is adhered to the flange 4. A motor shaft insertion hole 5 of a substantially square shape is formed at the center of the center core 2. A position regulating pin insertion hole 6 of a rectangular shape is formed in the center core 2 at a predetermined distance from the motor shaft insertion hole 5.
The magnetic disc 1 with the center core 2 is housed within a casing consisting of an upper shell 7 and a lower shell 8. These shells 7 and 8 are injection-molded from an ABS resin containing an antistatic agent, and are adhered together at the peripheries by ultrasonic sealing. The center core 2 is fitted with a small clearance into a circular opening 9 formed at the center of the lower shell 8. Four arc-shaped ribs 10 extend on the inner surface of the lower shell 8 concentrically with the opening 9, and corresponding arc-shaped ribs are also formed on the inner surface of the upper shell 7.
Liners 11 and 12 of unwoven fabric such as rayon are adhered to the inner surfaces of the upper and lower shells 7 and 8 by heat sealing or ultrasonic sealing. The liners 11 and 12 serve to automatically remove dust deposited on the magnetic disc 1 and prevent dropout of the disc during rotation, as well as to prevent abrasion and generation of static electricity of the magnetic disc 1. The liner 12 is adhered on the inner surface of the lower shell 8 through a tongue 13 of a synthetic resin, so that the liner 12 is securely urged against the magnetic surface of the magnetic disc 1.
Elongate holes 14, 15, 16 and 17 of identical shape are formed in the upper shell 7, the lower shell 8, the liner 11 and the liner 12 respectively to extend in the radial direction of the magnetic disc 1. When the upper and lower shells 7 and 8 are joined together, these elongated holes are registered with each other. Upon loading the magnetic disc into a magnetic disc recorder, a magnetic head is brought into contact with the magnetic disc 1 through the elongated hole 17 formed in the lower shell 8 and the elongated hole 16 formed in the liner 12. Similarly, a head pad is inserted into the elongated hole 14 formed in the upper shell 7 and into the elongated hole 15 formed in the liner 11.
Recesses 18 and 19 are formed on those parts of the upper and lower shells 7 and 8 which include the elongated holes 14 and 17, respectively. A U-shaped aluminum shutter 20 which has slits 21 and 22 of the same shape as that of the elongated holes 14 to 17 is slidably mounted such that it clips into the recesses 18 and 19.
As shown in FIG. 2B, a guide groove 23 is formed along the side edge of the lower shell 8. Three protuberances 24 project inwardly from the shutter 20 in correspondence with the guide groove 23. Therefore, the shutter 20 is guided along the guide groove 23 to establish the operating state and the non-operating state. Referring to FIGS. 2A and 2B, in the operating state the elongated holes 16 and 17 for head insertion, the elongated holes 14 and 15 for head pad insertion, and the slits 21 and 22 are all registered as indicated by the solid lines, and the magnetic disc 1 is exposed therethrough. On the other hand, in the non-operating state, the elongated holes 14 to 17 are closed and the magnetic disc 1 is covered by the shutter 20, as indicated by the dotted line. In this manner, the shutter 20 serves to protect the magnetic disc 1 and prevent introduction of dust.
An erroneous erasure prevention lug 25 is arranged at one corner of the lower shell 8. Information recorded on the magnetic disc 1 is protected if the lug 25 is removed. As shown in FIG. 2B, a pair of positioning holes 26 and 27 for positioning the magnetic disc device in a disc recorder are formed at two corners of the lower shell 8. At the other two corners of the lower shell 8 at which the positioning holes 26 and 27 are not formed, positions 28 and 29 indicated by hatched lines in FIG. 2B serve as reference surfaces. Thus, the magnetic device is supported at the reference position with reference to the four corners.
In the disc recorder shown in FIG. 3, four receiving pins 31 for receiving a magnetic disc device 30 as described above extend upright on a chassis 32. The top ends of two of the pins 31 are inserted in the positioning holes 26 and 27 of the lower shell 8, and the top ends of the remaining two pins 31 abut against the reference surfaces 28 and 29. The magnetic disc device is supported in a horizontal plane at a predetermined height by the pins 31, and recording or reproduction of digital or analog signals is performed in this state. A pivot plate 35 pivots about shafts 33 and 34. The magnetic disc device 30 is pressed from above by four pins 36 extending downward from the pivot plate 35. These press pins 36 are constantly biased downward by coil springs 37.